在 UIImageView 后面创建阴影的最佳方法是什么

The simplest thing to do is add a shadow layer to your image view:

CALayer             *layer = [CALayer layer];
CGRect              bounds = self.bounds;


layer.bounds = bounds;
layer.position = CGPointMake(bounds.size.width / 2 + 3, bounds.size.height / 2 + 3);
layer.backgroundColor = [UIColor colorWithWhite: 0.25 alpha: 0.55].CGColor;
layer.zPosition = -5;


[self.layer addSublayer: layer];

Be sure "Clip Subviews" is turned off for the view

There's a better and easier way to do this. UIImageView inherits from UIView so it has a layer property. You can access the layer's shadow properties and bam, you got a shadow.

If you have the UIImageView as an IBOutlet to a nib file, you can just implement the awakeFromNib e.g.

Objective-C

- (void)awakeFromNib {
imageView.layer.shadowColor = [UIColor purpleColor].CGColor;
imageView.layer.shadowOffset = CGSizeMake(0, 1);
imageView.layer.shadowOpacity = 1;
imageView.layer.shadowRadius = 1.0;
imageView.clipsToBounds = NO;
}

Don't forget to #import "QuartzCore/CALayer.h"

For Swift, you can go about it multiple ways. Create a class extension, subclass, or an imageView instance. Whichever the way, the process is the same in modifying the layers shadow property.

Swift 3

override func awakeFromNib() {
super.awakeFromNib()


imageView.layer.shadowColor = UIColor.purple.cgColor
imageView.layer.shadowOffset = CGSize(width: 0, height: 1)
imageView.layer.shadowOpacity = 1
imageView.layer.shadowRadius = 1.0
imageView.clipsToBounds = false
}

in additional to that, if you want to make white border and shadow you can use that code :

//shadow part
imageView.layer.shadowColor = [UIColor blackColor].CGColor;
imageView.layer.shadowOffset = CGSizeMake(0, 1);
imageView.layer.shadowOpacity = 1;
imageView.layer.shadowRadius = 1.0;
//white border part
[imageView.layer setBorderColor: [[UIColor whiteColor] CGColor]];
[imageView.layer setBorderWidth: 2.0];

Swift solution with extension. Subclassing is not required. Call myImage.addShadow() from viewDidLoad(). This should work for UIView and UIImageView.

extension UIView {


func addShadow() {
layer.shadowColor = UIColor.black.cgColor
layer.shadowOffset = CGSize(width: 0, height: 0)
layer.shadowOpacity = 0.5
layer.shadowRadius = 5
clipsToBounds = false
}
}

Swift 5.x

profileImageView.layer.cornerRadius = profileImageView.frame.size.width/2
profileImageView.clipsToBounds = false
profileImageView.layer.shadowColor = UIColor.black.cgColor
profileImageView.layer.shadowOpacity = 0.7
profileImageView.layer.shadowOffset =  CGSize(width: 2, height: 2)
profileImageView.layer.shadowRadius = 10